Generally, an injection apparatus for a molding machine moves an injection plunger forward in a sleeve with an injection cylinder and extrudes molding material (e.g., molten material) out of the sleeve into a cavity formed between molds (mold unit) to inject and fill the molding material into the cavity. The injecting and filling operation includes a low speed operation, a high speed operation, and a pressurizing operation. More specifically, in an initial state of the injection, the injection apparatus moves an injection plunger forward at a relatively low speed to prevent the inclusion of air in the molding material. Then, to shorten the molding cycle, the injection plunger is moved forward at a relatively high speed. Subsequently, the injection apparatus pressurizes the molding material in the cavity by applying force in the direction the injection plunger moves forward so that sink marks are not included in the molded product. Patent document 1 discloses an example of an injection apparatus (die cast machine) that realizes the operations of such an injection apparatus.
Referring to FIG. 6, the injection apparatus of patent document 1 includes a hydraulic circuit and executes hydraulic pressure control on the hydraulic circuit to perform the injection and filling operation. More specifically, in the injection apparatus, an injection cylinder 80 includes a head chamber 80a connected by a flow passage to a filling accumulator 82, which is in communication with a gas tank 81. The flow passage includes a pilot check valve 84 and a speed control valve 85. The filling accumulator 82 is supplied with hydraulic oil that is pressurized to a predetermined pressure by a hydraulic pump 83a. 
A flow passage, which is in communication with the speed control valve 85, is connected to a pressurizing operation accumulator 87, which is in communication with a gas tank 86. A flow passage connecting the filling accumulator 82, the pressurizing operation accumulator 87, and the head chamber 80a of the injection cylinder 80 includes a flow rate control valve 88. The flow rate control valve 88 regulates the flow rate of the hydraulic oil to control the movement speed of a piston in the injection cylinder 80.
In the injection apparatus of patent document 1, the low speed operation and the high speed operation supply the head chamber 80a of the injection cylinder 80 with the hydraulic oil accumulated in the filling accumulator 82 to move the piston 80c at a low speed or a high speed. The speed control valve 85 controls the movement speed of the piston 80c. The pressurizing operation is performed by supplying the head chamber 80a of the injection cylinder 80 with high-pressure hydraulic oil from the pressurizing operation accumulator 87. In this case, the flow rate control valve 88 regulates the flow rate of the hydraulic oil to control the pressurizing time.